Flapping neighbor adjacency

[Randyx]

Hi Guys,

Need your assistance. I created topology below. I created HSRP on R12 and R13 then EIGRP everywhere. After everything is configured. The adjacency between R12 and R14 keeps coming up and down. I noticed that all packets are being routed to R13. All interfaces have equal speed (10mbps / half duplex). I'm suspecting split-horizon but not 100% sure. 

Here are the configurations

R12

interface FastEthernet0/0
ip address 192.168.10.2 255.255.255.248
speed auto
duplex auto
standby 1 ip 192.168.10.1
standby 1 priority 110
standby 1 preempt
!
interface Serial0/0
no ip address
shutdown
clock rate 2000000
!
interface FastEthernet0/1
ip address 192.168.10.9 255.255.255.248
speed auto
duplex auto

!
router eigrp 1
network 192.168.10.0 0.0.0.7
network 192.168.10.8 0.0.0.3
no auto-summary
!

R13

interface FastEthernet0/0
ip address 192.168.10.3 255.255.255.248
speed auto
duplex auto
standby 1 ip 192.168.10.1
standby 1 preempt
!
interface Serial0/0
no ip address
shutdown
clock rate 2000000
!
interface FastEthernet0/1
ip address 192.168.10.22 255.255.255.252
speed auto
duplex auto
!

!
router eigrp 1
network 192.168.10.0 0.0.0.7
network 192.168.10.20 0.0.0.3
no auto-summary

R14

interface FastEthernet0/0
ip address 192.168.10.13 255.255.255.252
speed auto
duplex auto
!
interface Serial0/0
no ip address
shutdown
clock rate 2000000
!
interface FastEthernet0/1
ip address 192.168.10.10 255.255.255.252
speed auto
duplex auto

router eigrp 1
network 192.168.10.8 0.0.0.3
network 192.168.10.12 0.0.0.3
no auto-summary

R15
interface FastEthernet0/0
ip address 192.168.10.18 255.255.255.252
duplex auto
speed auto
!
interface Serial0/0
no ip address
shutdown
clock rate 2000000
!
interface FastEthernet0/1
ip address 192.168.10.21 255.255.255.252
duplex auto
speed auto

!
router eigrp 1
network 192.168.10.16 0.0.0.3
network 192.168.10.20 0.0.0.3
no auto-summary

R11
!
interface Loopback0
ip address 11.11.11.11 255.255.255.0
!
interface FastEthernet0/0
ip address 192.168.10.14 255.255.255.252
speed auto
duplex auto
!
interface Serial0/0
no ip address
shutdown
clock rate 2000000
!
interface FastEthernet0/1
ip address 192.168.10.17 255.255.255.252
speed auto
duplex auto

router eigrp 1
network 11.11.11.0 0.0.0.255
network 192.168.10.12 0.0.0.3
network 192.168.10.16 0.0.0.3
no auto-summary

[azibnaseem · Accepted solution]

spamguard006  

What I have observed from the configuration that you have miss-configured R12 Fa 0/1. Its subnet mask should be 252.

interface FastEthernet0/1
ip address 192.168.10.9 255.255.255.248.

It should be 255.255.255.252.

You have also advertised network 192.168.10.8 0.0.0.3 in Eigrp.

Make these changes if can help.

Regards'

[Randyx]

Wow!! I completely missed it. I've been troubleshooting this for a day. Darn!! Thanks for everyone's help..appreciate it!

[azibnaseem]

HI spamguard006  '

Very glad to hear that your problem is resolved.

Regard'

[Deepak Kumar]

Hi, 

Set your interface speed and duplex manually and check your Subnet configuration. Your problem will resolved. I was faced same issue.

Reards, 

Deepak Kumar